The present invention relates to a trimming tool for trimming drawn parts over their complete periphery and for the simultaneous transverse cutting of the waste strip which has been cut off.
A known trimming tool is disclosed, for example, in German Offenlegungsschrift No. 4,034,278, and consists of a lower tool accepting the drawn part and defining its position and a two-part upper tool which can be lowered on the drawn part to be trimmed, which is inserted into the lower tool. A lower trimming shear-cutter following the contour of the trim and corresponding in three dimensions to the edge shape of the drawn part placed thereupon is formed on the lower tool. The contact surface acting to support the drawn part on the lower trimming shear-cutter is located within the closed shear edge trace of the lower trimming shear-cutter. The two-part upper tool is formed from a holding-down part and an upper trimming shear-cutter. In its plan and surface shape, the holding-down part corresponds negatively to the lower trimming shear-cutter and comes into contact with the drawn part first. The outermost contour line limiting the contact surface of the holding-down part towards the outside coincides with the shear edge extent of the lower trimming shear-cutter. The upper trimming shear-cutter surrounds the holding-down part and is guided so that it can move relative to it in the shear direction. Its shear edge likewise coincides with the shear edge extent of the lower trimming shear-cutter but only touches the inserted drawn part after a time delay relative to the contact by the holding-down part and, interacting with the lower trimming shear-cutter, shears off, all round, the edge of the drawn part which has to be trimmed.
For transverse cutting of the waste strip with the known trimming tool, a plurality of lower transverse cutters are mounted in fixed location; outside the shear edge of the lower trimming shear-cutter and transverse to it with their shear edge offset downwards. Pivotable shear bodies are mounted on the upper tool offset relative to the transverse cutters in the peripheral direction. A shear edge located congruently with the shear edge of the transverse cutter is formed on these shear bodies. In order to cut the waste strip transversely after it has been separated from the workpiece, the shear body is pivoted against the action of return structure by lowering the upper tool such that the waste strip is cut in the transverse direction.
This known appliance for the transverse cutting of the waste strip is, however, costly. On one hand, the space requirement for the pivotable shear body is large, as a consequence of which the access for inserting and removing the workpiece from the tool is also obstructed. On the other hand, the pivot bearings and the return structure of the shear body require frequent maintenance and repair because they are extremely heavily loaded. In addition, the retrofitting of tools already available with such a transverse cutting appliance, if possible at all, is awkward and expensive.
Another trimming tool with an integrated transverse cutting device is disclosed in German Offenlegungsschrift No. 4,035,857. There, the transverse cutters are pivotably supported in the trimming shear-cutter of the upper tool and extend right up to the shear edge of the trimming shear-cutter; their transverse edge forms part of the shear edge for the trim cut. The pivoting axis of the transverse cutter is located at the same height as the end shear edge which effects the cut. For the transverse cutting of the waste strip separated from the drawn part, the pivotable shear-cutters are pivoted downwardly in a direction coincident with the downwards motion of the upper tool, the waste strip being respectively sheared off against a lower, transverse cutter in a fixed location which, however, has to be arranged offset downwards relative to the lower dead center of the upper tool so that it does not interfere with the peripheral trimming of the workpiece which has to take place first. Because of the pivoting motion of the transverse cutter, the outermost, workpiece end of the shear edge of the transverse cutter moves on a circular arc which becomes more and more distant from the inner edge of the waste strip with increasing downward motion. Consequently, it is not possible to achieve the result that the transverse cutter shears through the waste strip completely and right up to the inner, peripherally extending cut edge. In the known trimming tool, the result is rather that a small part of the cut is torn. During this tearing, however, small workpiece particles are often released from the separating location of the waste strip and fly around in an uncontrolled manner so that they can pass into the tool and onto the workpiece where, during further processing, they leave impressions which cannot be removed, or can only be removed with an unacceptable level of rework.
An object of the present invention is to achieve complete and fragment-free transverse cutting of the waste strip by way of a low-maintenance, reliable tool which does not limit the space for introducing and removing the workpiece.
The foregoing object has been achieved, according to the present invention, by a trimming tool having a lower tool portion accepting and defining a position of the drawn part, which lower tool has a lower trimming shear-cutter corresponding with a desired trim contour and corresponding in three dimensions to an edge shape of the drawn part placed thereon, a support surface for supporting the drawn part on the lower trimming shear-cutter located within a closed shear edge trace of the lower trimming shear-cutter. A multi-part upper tool is arranged to be lowered onto the drawn part to be trimmed to be inserted into the lower tool, and a holding-down part in the upper tool is arranged to make contact initially and with a defined force on the drawn part configured to negatively corresponding in a plan and surface shape to the lower trimming shear-cutter and whose outermost contour line limiting a contact surface thereof towards the outside coincides with a shear edge extent of the lower trimming shear-cutter. An upper trimming shear-cutter is provided in the upper tool so as to surround the holding-down part and be movably guided relative thereto in the shear direction and whose shear edge coincides with the shear edge extent of the lower trimming shear-cutter but only touches the inserted drawn part after a time delay relative to the contact by the holding-down part and, interacting with the lower trimming shear-cutter, shears off, all around, the waste strip of the drawn part which has to be trimmed. A plurality of lower transverse cutters is arranged in accordance with the present invention outside the shear edge of the lower trimming shear-cutter and is distributed around the periphery and mounted in a fixed location transverse to the periphery, the shear edge of the transverse cutters reaching but located offset downward relative to the shear edge of the lower trimming shear-cutter. A plurality of upper transverse cutters is mounted on the upper trimming shear-cutter, and has edges respectively congruent with the shear edges of the lower transverse cutters, cutter bodies of the upper transverse cutters being located offset relative to one another in the peripheral direction, the shear edges of the upper transverse cutters reaching to the shear edge of the upper trimming shear-cutter, and the shear edge of the upper trimming shear-cutter being interrupted, in the region of each upper transverse cutter, by a dimension corresponding at least to the cutter body thickness of the lower transverse cutter.
A make-up cutter is provided in the region of the interruption of the shear edge of the upper trimming shear-cutter, so as to fill the interruption and is movably guided within the upper trimming shear-cutter in the shear direction and is held by a controllable support in a lower rest position relative to the upper trimming shear-cutter, the shear edge of which, as viewed both in the shear direction and transverse thereto, follows the remainder of the contour extent of the upper trimming shear-cutter in the rest position and effects an uninterrupted extent of the shear edge of the upper trimming shear-cutter.
The support for the make-up cutter is configured either controllably or flexibly as a function of the stroke such that, at the latest, when the make-up cutter of the upper transverse cutter makes contact on the lower transverse cutter, the support frees the make-up cutter so that the make-up cutter can automatically escape upwards within the upper trimming shear-cutter sufficiently far for the shear edge of the upper transverse cutter to be able to be freed over its complete length as far as the shear edges of the trimming shear-cutter.
The transverse cutting in the tool of the present invention takes place by rectilinear further motion of a transverse cutter integrated in a fixed location in the upper tool. Its shear edge is freed in sufficient time by an escape motion of a make-up cutter. This escape motion can take place in both a controlled manner and by force storage elements, in particular by a spring. The make-up cutter permits, on one hand, a complete and clean trim cut to be carried out on the workpiece and, on the other hand, permits the shear edge of the transverse cutter to extend right up to the trim shear edge. Because of the rectilinear downward motion of the transverse cutter, the waste strip is also sheared off cleanly and without cracks as far as the innermost trim cut edge. Uninterrupted operation is also possible because of the integration of the transverse cutter in a fixed location in the upper tool.
The transverse cutting of the waste strip, furthermore, takes place by components which are substantially smaller compared with the transverse cutting appliance pointed out in the state of the art. The access to the workpiece with the tool open is not impaired by this. A further advantage of the invention is that the appliance according to the invention can be manufactured at low cost and, in addition, tools already existing can also be retrofitted at low cost.